Standard format for Enumeration

[dskrvk]

Would it be useful to provide a standard format for values of an arbitrary Enumeration type?

I have a working implementation, though it relies on an implicit type evidence of the specific enum type provided by the user. I could use reflection instead, but that seems less desirable.

[dkowis]

I'd like to see said implementation, even if it's not part of the project, I could use it :)

[dkowis]

Since I ended up finding this after digging around on the internet for an example, I'll paste the example I found

import spray.json.{DeserializationException, JsString, JsValue, RootJsonFormat}

/**
  * Based on the code found: https://groups.google.com/forum/#!topic/spray-user/RkIwRIXzDDc
  */
class EnumJsonConverter[T <: scala.Enumeration](enu: T) extends RootJsonFormat[T#Value] {
  override def write(obj: T#Value): JsValue = JsString(obj.toString)

  override def read(json: JsValue): T#Value = {
    json match {
      case JsString(txt) => enu.withName(txt)
      case somethingElse => throw DeserializationException(s"Expected a value from enum $enu instead of $somethingElse")
    }
  }
}

Use like:

implicit val enumConverter = new EnumJsonConverter(YourEnum)

[davideicardi]

@dkowis I have created a PR, #336, based on your code to add it as an example.

[waagnermann]

@dkowis I have created a PR, #336, based on your code to add it as an example.

But it's not PR to code itself, it's just PR to README.md :)
Can collaborators introduce this feature (support for Enumeration formats) in future updates?